I eventually got this working. Here is the approach for everybody who intends to load Orion-managed files from another web application:

Make sure that you can load the transient closure of orion/bootstrap.js (orion.core plugin) into your JS code. I did this with adding the corresponding JS files to a Utility plugin named 'orion' to allow requirejs to resolve dependencies. There may be other, more elegant ways.

Code to load the plugin and retrieve the file is below whereby

* uri is the file URI and
* Utils is a auxiliary class for logging. You may use console.log() instead.